Helical structures of poly(D-L-peptides). A conformational energy analysis

Area of Science:

• * Computational chemistry
• * Polymer science
• * Structural biology

Background:

• * Poly(D-L-peptides) can adopt various helical conformations.
• * Understanding these structures is crucial for predicting peptide behavior.
• * Conformational energy calculations are key to determining stable structures.

Purpose of the Study:

• * To calculate and compare the conformational energies of different helical structures in poly(D-L-peptides).
• * To investigate the existence and characteristics of potential structural variants (goniomers).
• * To assess the biological implications and computational utility of predicted goniomers.

Main Methods:

• * Utilized conformational energy calculations to model peptide structures.
• * Focused on poly(D-alanine-L-alanine) as a model sequence.
• * Analyzed alpha, piDL, and pipiDL helical structures, including potential variants.

Main Results:

• * Found minimal energy differences (<1 kcal/mol residue) among various helical structures for poly(D-alanine-L-alanine).
• * Predicted two distinct structural variants, termed goniomers, for certain piDL helices.
• * Goniomers exhibit reversed conformational angles but maintain similar helical parameters and screw sense.

Conclusions:

• * Poly(D-L-peptides) exhibit energetically similar helical structures, suggesting conformational flexibility.
• * The discovery of goniomers provides a novel biological implication and a critical test for computational energy calculations.
• * Further research into goniomers can refine predictive models for peptide structure and function.